Engine compression operated piezoelectric ignition system



Nov. 2, 1965 J. M. FARRELL 3,215,133

ENGINE COMPRESSION OPERATED PIEZOELECTRIC IGNITION SYSTEM Filed NOV. 22,1963 2 Sheets-Sheet 1 INVENTOR. JOHN H. FARRELL BY @RW Hi5 ATTORNEY Nov.2, 1965 J. M. FARRELL 3,215,133

ENGINE COMPRESSION OPERATED PIEZOELECTRIC IGNITION SYSTEM Filed Nov. 22,1963 2. Sheets-Sheet 2 INVENTOR. JOHN T1- FARRELL BY @RW HIS ATTORNEYENGINE COMPRESSION OPERATED PIEZO- ELECTREC IGNITIGN SYSTEM John M.Farrell, Detroit, Mich, assignor to General Motors Corporation, Detroit,Mich, a corporation of Delaware Filed Nov. 22, 1963, Ser. No. 325,610

8 Claims. (Cl. 123-148) This invention relates to ignition systems forinternal combustion engines and more particularly to an ignition systemwherein a piezoelectric crystal or element is used as a source ofvoltage to directly fire a spark plug and wherein a piezoelectriccrystal is stressed by engine compression.

It is well-known to those skilled in the art that a piezoelectriccrystal can be stressed and will provide a high output voltage that iscapable of directly firing a spark plug without the use of ignitioncoils or batteries. In the past piezoelectric crystal has been stressedthrough a cam and follower mechanism and the cam is driven insynchronism with the engine so that the firing of the spark plug occursat some point of rotation of the cam.

In contrast to the cam and follower arrangement for stressing apiezoelectric crystal, it is an object of this invention to provideignition systems wherein the pressure produced during the compressionstroke of an internal combustion engine is used to stress thepiezoelectric crystal to cause a firing of a spark plug at apredetermined pressure within the cyclinder of the engine. 7

Another object of this invention is to provide a combined spark plug andpressure operated piezoelectric spark source which can be fitted into acylinder of an internal combustion engine.

Still another object of this invention is to provide a piezoelectricignition system wherein the crystal is stressed through a link or leverWhich is operated by engine compression.

Another object of this invention is to provide a piezoelectric ignitionarrangement wherein the piezoelectric crystal is stressed by enginecompression and wherein a variable pressure can be applied to thepiezoelectric crystal for engine timing by means of a vacuum control orsimilar engine or manifold vacuum adjusted device.

Another object of this invention is to provide an ignition systemwherein the piezoelectric element is stressed by an electricallyenergizable device such as an electromagnet and wherein the energizationof the device depends upon a timing control and a pressure responsivecontrol which operates in accordance with cylinder pressure.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein referred embodiments of the present invention areclearly shown.

In the drawings:

FIGURE 1 illustrates a piezoelectric ignition apparatus where thepiezoelectric crystal or element is stressed by engine cylinderpressure.

FIGURE 2 illustrates a piezoelectric ignition apparatus where the devicefor stressing the crystal and the spark plug are combined into one unit.

FIGURE 3 illustrates an arrangement wherein the piezoelectric crystal isstressed through a lever which is moved in accordance with cylinderpressure.

FIGURE 4 illustrates an arrangement for adjusting the pressure on apiezoelectric crystal through the use of a vacuum timing control.

FIGURE 5 illustrates a piezoelectric ignition system where thepiezoelectric crystal or element is stressed by an electromagnet andWherein the circuit for the electro- United States Patent ice magnet iscontrolled by an engine driven timing device and by engine cylinderpressure.

Referring now to FIG. 1, the reference numeral 10 designates thecylinder of a four cycle internal combustion engine. The referencenumeral 12 designates a reciprocable piston of the engine which isconnected with a crank shaft in the usual manner. The exhaust valves andintake valves for the engine are not illustrated but they areconventional. I

The cylinder 10 has a threaded opening which receives a housing 14. Thehousing 14 contains a reciprocable piston 16, one end of which engages apart 15 that engages a piezoelectric crystal or element 18. Thepiezoelectric crystal or element 18 is capable of developing an outputvoltage when it is stressed.

An adjusting screw 20 is provided for adjusting the initial forceapplied to the crystal 18 and this adjusting screw is threaded into oneend of the housing 14. One side of the crystal is connected with aterminal of a spark plug 22 by a conductor 24. The spark plug isthreaded into one wall of the cylinder 10 as is apparent from FIGURE 1.The opposite side of the piezoelectric crystal 18 is grounded eitherthrough part 15 and the piston 16 or if desired, through a conductorwhich engages the housing 14. The output terminals of the piezoelectrictal 18 is grounded either through part 15 and the piston electrodes ofthe spark plug 22.

As the piston 12 reciprocates in the cylinder 10, pressure is developedwithin the cylinder which will force the piston 16 upwardly during thecompression stroke of the engine. At some predetermined pressure, thecrystal 16 is stressed sufliciently to cause a firing of the spark plug22 since the crystal develops a high output voltage when it ismechanically stressed. The timing of the spark will depend upon thepressure in the cylinder 10 and by the preloading of the piezoelectricelement 18 by the adjusting screw 20. Thus as the preloading of thepiezoelectric element 18 is increased, less pressure in the cylinder 10is required to stress the piezoelectric element 18. It therefore is seenthat the timing of the spark can be varied by varying the preloading ofthe piezoelectric element 18. The adjusting screw is insulated from thetop side of the piezoelectric crystal 18 so that the top side of thecrystal is not grounded.

Referring now to FIGURE 2, an ignition apparatus is illustrated which issimilar to that shown in FIGURE 1 but wherein the spark plug and sparksource are built into one unit. In FIGURE 2, a metal housing 26 isthreaded into the cylinder 10. The housing 26 carries a spark electrode28. Another spark electrode 30 is provided which is connected with aconductive plate 32 which engages one side of the piezoelectric crystal34.

An annular piston 36 is provided which is insulated by insulatingmaterial 38 from the plate 32. The top end of the piezoelectric crystalengagesa metal plate 40 which in turn engages an adjusting screw 42threaded into the housing 26. The adjusting screw is once more used topreload the piezoelectric crystal 34.

With the arrangement of FIGURE 2, the top end of the piezoelectriccrystal 34 is electrically connected with the housing 26 through thescrew 42 and therefore is connected with electrode 28. The opposite sideof the piezoelectric crystal 34 is electrically connected with electrode31).

When the cylinder 10 has a predetermined pressure, the piston 36 isforced upwardly to stress the crystal 34 an amount sutficient to causean arc to jump between electrodes 28 and 30. As the pressure reduces inthe cylinder 10, the crystal 34 is no longer stressed. The timing of theare between electrodes 28 and 30 again depends upon the pressuredeveloped in the cylinder and upon the preloading of the crystal 34 bythe screw 42.

FIGURE 3 illustrates a system where the piezoelectric crvstal and thespark gap are built into one unit and where the crystal is stressed by alever that is operated by cylinder pressure. In FIGURE 3, a piston 44can reciprocate within a housing 46 threaded into an opening in cylinder10. The lever 48 is pivoted at 50 and one end of this lever engages thepiston 44. The opposite end of lever 48 has an opening which receives anadjusting screw 52. The adjusting screw can apply pressure to thepiezoelectric element 54 which is located within housing 56. The housing56 is connected with one electrode 58 of a spark gap, the otherelectrode 60 being disposed within an insulator 62 fitted within thehousing 56. The top end of the piezoelectric crystal 54 is electricallyconnected with housing 56 and to electrode 58 by conductor 59 or throughscrew 52. The lower end of the piezoelectric crystal 54 is connectedwith the electrode 60 so that the output voltage of the piezoelectriccrystal 54 is impressed across electrodes 58 and 60.

With the arrangement of FIGURE 3, the piston 44 is moved upwardly byengine cylinder pressure and a force is transmitted to the crystal 54 tostress it through the lever 48. A timing adjustment can be made with thearrangement of FIGURE 3 by adjusting the screw 52 relative to the lever48.

FIGURE 4 illustrates an arrangement for varying the timing of the firingof a spark plug in a piezoelectric apparatus. In FIGURE 4, thepiezoelectric element 64 is disposed between a piston 66 and a part 68.A wedge 70 is located between parts 68 and 72. The part 72 can beadjusted through a preloading adjusting screw 74. It will be appreciatedthat movement of the wedge 70 will vary the preloading of thepiezoelectric element 64. By varying the preloading of the crystal, thepoint at which the element 64 is stressed to fire a spark plug isaccordingly varied.

In FIGURE 4, the wedge 70 is moved in accordance with conditions ofoperation of the engine. Thus the wedge 70 can be connected with thediaphragm 76 of a vacuum unit 78 which is connected to the intakemanifold of the engine. It is apparent that the wedge 70 could beadjusted in accordance with other engine conditions.

The arrangement of FIGURE 4 can be used with the other systems describedabove and provides a means for varying engine timing in accordance withconditions of operation of the engine.

Referring now to FIGURE 5, a piezoelectric ignition system isillustrated wherein the piezoelectric crystal 80 is stressed by anelectromagnetic actuator 82. The actuator 82 has, for example, areciprocable armature 81 engaging one side of the crystal 80, theopposite side of the crystal engaging a fiXed support 83. Theelectromagnetic actuator 82 has a coil winding 84. One end of the coilwinding 84 is connected with a pressure operated switch 86 which iscapable of connecting the conductor 88 to ground whenever the pressurein cylinder 10 reaches a predetermined value.

The conductor 90 which is connected with the opposite side of coilwinding 84 is connected with a conductor 92 and a pair of breakercontacts 94. The breaker contacts 94 are opened and closed by a cam 96which is driven by the crank shaft of the engine. The closing andopening of the contacts 94 are therefore synchronized with the positionof the pistons in a multi-cylinder engine. The opposite side of thebreaker contacts 94 are connected with a conductor 98 and this conductoris connected to one side of a battery 100. The opposite side of thebattery 100 is grounded.

The conductor 92 is connected with conductors 102 and 104 which areintended to illustrate conductors that can feed other electromagneticactuators of the type designated by reference numeral 82. Thus it iscontemplated 4 with the system of FIGURE 5 that each cylinder of theengine will have an electromagnetic actuator and a piezoelectric crystaland that the circuit for each electromagnetic actuator will employ apressure switch of the type designated by reference numeral 86. Thebreaker points 94, however, will be common to one side of all of thecoil windings of the respective electromagnetic actuators.

It is seen from FIGURE 5 that one side of the piezoelectric crystal isgrounded whereas the opposite side of this crystal is connected with theelectrode of a spark plug 106 which has its spark gap located in theengine cylinder 10.

With the apparatus of FIGURE 5, the spark plug 106 will be firedwhenever the piezoelectric crystal is stressed and the crystal will bestressed only when the coil winding 84 is energized. The coil winding 84can only be energized when breaker contacts 94 and the contacts ofpressure switch 86 are simultaneously closed. The arrangement is suchthat the pressure switch 86 closes before the timing cam 96 permits aclosure of breaker contacts 94. When both contacts 94 and the contactsof the pressure switch 86 are closed, the spark plug 106 will be firedsince at this time the crystal 80 is stressed by the electromagneticactuator 82. The cam 96 and the breaker contacts 94 can be of the sametype as is provided in a conventional distributor in which case, theclosing of contact 94 can be controlled by the centrifugal advance andvacuum advance mechanisms of a distributor.

As pointed out above, the conductor 92 and conductors 102 and 104 arefor feeding electromagnetic actuators of the type designated byreference numeral 82. Thus in a multi-cylinder system, there will be asmany electromagnetic actuators and crystals and pressure operatedswitches as there are cylinders for the engine, but the electromagneticactuators are commonly controlled by one set of breaker contacts 94.

While the embodiments of the present invention as herein disclosed,constitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In combination, an internal combustion engine having a cylinder and apiston which reciprocates therein, an element separate from said pistonshiftable by engine cylinder pressure, a spark discharge device havingelectrodes located in said cylinder, a piezoelectric crystalelectrically connected with said spark discharge device for applyingspark firing energy directly to said spark discharge device, and a leverinterposed between said shiftable element and said piezoelectric crystalfor stressing said crystal when engine cylinder pressure reaches apredetermined value.

2. An ignition system for an internal combustion engine having acylinder and a reciprocable piston comprising, a spark discharge devicehaving electrodes located within said cylinder, a piezoelectric crystal,an actuating means for stressing said piezoelectric crystal, meansdirectly electrically connecting said piezoelectric crystal and saidspark discharge device whereby voltage pulses developed by said crystalare used to directly fire said spark discharge device, a pressureresponsive control means responding to pressure conditions in saidcylinder, a timing control means operating in synchronism with saidengine, and means connecting said timing control means, said pressureresponsive means and said actuating means whereby the actuation of saidactuating means is controlled by said timing control means and saidpressure responsive means.

3. The ignition system according to claim 2 where the actuating means isan electromagnet and where said timing control means and pressureresponsive means are switches for controlling the energization of theelectromagnet.

4. An ignition system for an internal combustion en gine comprising, aspark plug for firing the combustible mixture of the engine, apiezoelectric crystal, an electromagnetic actuator having a coil windingfor stressing said piezoelectric crystal, means directly electricallyconnecting said crystal and said spark plug whereby voltage pulsesdeveloped by said crystal are used to directly fire said spark plug, apressure responsive switch operated in accordance with engine cylinderpressure, a timing switch operated in synchronism with said engine, asource of voltage, and means electrically connecting said timing switch,said pressure responsive switch and said coil winding in a seriescircuit across said source of voltage.

5. In combination, an internal combustion engine having a cylinder and apiston that reciprocates therein, a shiftablc element separate from saidpiston having at least one face subjected to cylinder pressure wherebysaid element is shifted by engine cylinder pressure, a spark dischargedevice having electrodes located in said cylinder, a piezoelectriccrystal electrically connected with said spark discharge device forapplying spark firing energy to said spark discharge device, and a leverinterposed between said shiftable element and said piezoelectric crystalfor stressing said crystal when engine cylinder pressure reaches apredetermined value.

6. In combination, an internal combustion engine having a cylinder and areciprocable piston, a spark discharge device for firing the combustiblemixture in said cylinder, a piezoelectric crystal connected with saidspark discharge device for directly firing said spark discharge devicefrom the voltage developed by said crystal when it is stressed, anelement separate from said piston shiftable by engine cylinder pressureand operable to stress said piezoelectric crystal, and means for varyingthe preloading of said piezoelectric crystal in accordance with acondition of operation of said engine.

7. The combination according to claim 6 wherein the means for varyingthe preloading of the crystal includes a wedge means that is adjustablein accordance with a condition of operation of said engine.

8. In combination, an internal combustion engine having a cylinder and apiston that reciprocates therein, an element separate from said pistonshiftable by engine cylinder pressure, a spark discharge device havingelectrodes located in said cylinder, a piezoelectric crystalelectrically connected with said spark discharge device for applyingspark firing energy directly to said spark discharge device, and forcetransmitting means interposed between said shiftable element and saidpiezoelectric crystal for transmitting the force developed by cylinderpressure to said crystal when engine cylinder pressure reaches apredetermined value, and means for varying the efiective length of saidforce transmitting means.

References Cited by the Examiner UNITED STATES PATENTS 2,068,744 1/37Gutzke 123-148 2,248,574 7/41 Knight 123-148 2,717,916 9/55 Harkness123-148 2,852,590 9/58 Fremon 123-148 RICHARD B. WILKINSON, PrimaryExaminer.

6. IN COMBINATION, AN INTERNAL COMBUSTION ENGINE HAVING A CYLINDER AND ARECIPROCABLE PISTON, A SPARK DISCHARGE DEVICE FOR FIRING THE COMBUSTIBLEMIXTURE IN SAID CYLINDER, A PIEZOELECTRIC CRYSTAL CONNECTED WITH SAIDSPARK DISCHARGE DEVICE FOR DIRECTLY FIRING SAID SPARK DISCHARGE DEVICEFROM THE VOLTAGE DEVELOPED BY SAID CRYSTAL WHEN IT IS STRESSED, ANELEMENT SEPARATE FROM SAID PISTON SHIFTABLE BY ENGINE CYLINDER PRESSUREAND OPERABLE TO STRESS SAID PIEXOELECTRIC CRYSTAL, AND MEANS FOR VARYINGTHE PRELOADING OF SAID PIEZOELECTRIC CRYSTAL IN ACCORDANCE WITH ACONDITION OF OPERATION OF SAID ENGINE.